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Questions from Students

A couple of weeks ago, I visited Dodd Elementary in Little Rock. After I left, the students wanted more information and sent me several questions. I thought, rather than respond to them individually, I would post the answers here.

Did saber-toothed tigers live at the same time as mammoths in the Ice Age? How old are mammoths?

Yes, they did! They even lived together in Arkansas during the Ice Ages, along with the more commonly found mastodons (which were like the mammoths, but a bit smaller (about the size of modern elephants) and were more adapted for forests than the grassy plains preferred by the mammoths.

What most people refer to as the Ice Age was in fact a series of almost a dozen times in which the glaciers expanded to cover much more land than they do now. This period lasted from about a million years ago to 11-12,000 years ago during what is called the Pleistocene Epoch.

There were actually many different species of saber-toothed cats. The most commonly known is one called Smilodon, which lived between 2,500.000  years ago to about 10-12,000 years ago.

The first mammoths appeared around 6,000,000 years ago, but the Woolly mammoths and the Columbian mammoths (the type that lived in Arkansas), first appeared about 400,000 years ago. They came south from Canada into the United States about 100,000 years ago. While they died out in North America almost 12,000 years ago, there were a few that lived on Wrangel Island near Russia until less than 5,000 years ago.

I wanted to know if cavemen were alive because didn’t the dinosaurs eat them?

All the dinosaurs (except birds) died out over 65,000,000 years ago, but the first humans only appeared around 200,000 years ago. So humans and dinosaurs were separated by an enormous amount of time and never lived together. Humans did live alongside the mammoths and saber-toothed cats during the Ice Ages, though. Humans killed and ate mammoths and humans and saber-toothed cats killed each other (we don’t know if humans ate the saber-toothed cats, but we’re pretty sure they ate us).

How old is coral?

Coral is very, very, old. The first corals appeared over 500,000,000 years ago. However, none of these early types of coral still exist. They all went extinct (died out) and were replaced by types of coral that evolved (descended) from them. The modern corals that you can see today first appeared in the Triassic Period roughly 200,000,000 years ago (the first dinosaurs appeared about 240,000,000 years ago).

How big is a T. rex egg?

No one knows! No T. rex eggs have ever been found. We can guess they were up to a foot long and up to five inches wide, but that is just a guess based on what we know of eggs that have been found from its distant relatives. What we do know is that T. rex babies were a lot smaller than the adults would have been no bigger than a small turkey.

How long is a sea spider?

fossil_focus_pycno_4Sea spiders, or pycnogonids (pic-no-go-nids), can grow up to 25 cm (10″). They can be found in the southern oceans today. Fossils of sea spiders are rare, but have been found as far back as the Cambrian Period almost 500,000,000 years ago. Even though they look something like spiders, while they are arthropods like spiders, they are not really spiders and occupy their own group within the arthropods. They are very strange animals, with most of their organs in their legs.

Eurypterus-remipes-LI think you may have been referring to a different animal though, the sea scorpions, which was part of the fossil collection we saw in class. Even though they are called scorpions, they are not true scorpions, although they are related to them. These animals, called eurypterids (your-ip-tur-ids), were mostly no more than 30 cm (12″), but could get almost 2.5 meters (8′), making them the biggest arthropods ever known. The earliest fossils we have found were dated at 467,000,000 years, but they may have first appeared over 500,000,000 years ago. They died out at the end of the Permian Period just over 250,000,000 years ago, along with most of the life on the planet at the time.

What is the shortest sea dinosaur?

While there were sea-going reptiles, there were no sea-going dinosaurs that we know of. The closest that we know of right now were the spinosaurs, which spent much of its time wading in relatively shallow water. These dinosaurs were huge, some of them approaching 15 m (50′) or more, with the smallest ones only a modest 8 m (26′).

Of the sea-going reptiles, the most common ones were the dolphin-shaped ichthyosaurs (ick-the-o-sores), the lizards called mosasaurs (literally lizard, they evolved from monitor lizards like the Komodo dragon),  the generally short-necked and big-headed pliosaurs (ply-o-sores), and the long-necked plesiosaurs (please-e-o-sores, for the purists, plesiosaur can also refer to both pliosaurs and the more traditional plesiosaurs because the larger group containing pliosaurs and plesiosaurs is named after the plesiosaurs. yes, it is a bit confusing). And of course we can’t forget the sea-going crocodiles called metriorhynchids (met-re-o-rine-kids).

The smallest ichthyosaur, or “fish-lizard” named Cartorhynchus (cart-0-rine-cuss) was less than 0.5 m (15″) long. it was also the oldest known one at almost 250,000,000 years old. You may notice that the picture below says the smallest was 70 cm, but an even smaller one was found.

Palaeontology_Ichthysaur

Dallasaurus (“Dallas lizard”), the earliest known mosasaur, was also the smallest mosasaur at no more than 1 m (3′).

The smallest plesiosaur was just over 1 m (3′).

Thalassiodracon, or “sea dragon”,  probably the smallest known and most primitive pliosaur, was 1.5-2 m (5-6.5′), so slightly bigger than its relatives, the plesiosaurs. All of the marine (sea-going) crocodilians were more than 2 m (6 ‘) and would have eaten the others, so we can rule them out for shortest marine reptile from the Mesozoic Era during the age of dinosaurs.

There is another group of marine reptiles that was also common during the Mesozoic, although they are not so widely known. The thallatosaurs, which literally means “ocean lizard” were as small as 1 m (3′). Finally, there was a sea turtle-like group called placodonts, of which the smallest were just under 1 m (3′).

Notice that most of them all start off at roughly 1 m, except for the ichthyosaurs, which started off at less than half of that, so the winner for shortest sea reptile of the dinosaur age is the ichthyosaur named Cartorhynchus.

What is the longest sea dinosaur?

The undisputed king of the marine reptiles was the ichthyosaur named Shonosaurus, also known as Shastasaurus, which reached 23 meters (75 feet).

shastasaurus-size

Still not the largest known individual of the species.

jurassicworld mosasaur

Jurassic World mosasaur, still not as big as Shonisasaurus

The longest mosasaur is, coincidentally, Mosasaurus itself, potentially reaching lengths of 18 meters (59 feet), so not as big as Shonosaurus. This animal used to live in Arkansas. According to the most official statements, the mosasaur in Jurassic World was 22 meters (72 feet), so bigger than the real ones, but not by a terribly large degree, and still smaller than Shonisaurus.

The longest pliosaur was no more than 18 meters (59 feet), while the longest plesiosaur was no more than 15 meters (49 feet), so none of them come close.

 

How did they breathe underwater?

It does seem like animals who live in the sea should be able to breathe underwater, doesn’t it? But the aquatic (a fancy word for living in the water) reptiles didn’t. Like all reptiles, they had to come up to the surface to breathe. This is true for any reptile that swims in the ocean, including sea turtles and marine iguanas. The same is true for their distant relatives, the birds. Penguins have to breathe air, even though they can dive deep. It is also true for all mammals, such as whales and dolphins. So how do they dive underwater and stay underwater for so long? They hold their breath, just like we do when we swim. Only they are much better at it than we are and can hold their breathe for a long time.

What is the longest land dinosaur?

That is an excellent question. The problem is that we have no fully complete skeletons of the largest dinosaurs, so we have to estimate their sizes from the bones we have.

Longest_dinosaurs_Scott_Hartman_Ken_Carpenter_Steveoc_86_Dinoguy2_700

As you can see on the chart above, there are several dinosaurs that are similar sized. Diplodocus and Supersaurus got up to 33.5 meters (110 feet). Argentinosaurus got upwards of 35 meters (115 feet) or more. Bruhathkayosaurus (Bru-hath-kay-o-sore-us) was possibly around this size as well, but the fossil material is too little to get a good estimate and what we had has disappeared. However, the American Museum of Natural History in New York has recently put on display the largest dinosaur ever displayed and possibly the largest dinosaur ever known at over 37 meters (122 feet).It doesn’t even have a name yet and is just called the AMNH titanosaur. Of course, the biggest dinosaur ever found is so little known that it has become almost mythical. Amphicoelias has been estimated to have been  as long as 58 meters (190 feet). Unfortunately, all that was found of this animal was a few bones, including a vertebra that stood 2.7 meters (8.9 feet) tall. The bones were very fragile, in very poor condition, and were preserved in mudstone, which crumbled easily. All of the fossils vanished (possibly crumbled away and swept out), so all we have left is a few drawings and measurements of the bones.

How big was Apatosaurus?

According to the fossils we have, Apatosaurus typically got around 22 meters (72 feet), but could have gotten as long as 27.5 meters (90 feet). Weight is a very difficult thing to estimate for many reasons, but most estimates place an adult Apatosaurus somewhere between 20-40 tons (40,000-80,000 pounds, 18000-36000 kg), or about the weight of 4-8 adult elephants.

apatosaurus-size

Illustratration by Darren Pepper, http://www.Prehistoric-Wildlife.com

What is the shortest land dinosaur? What is the smallest dinosaur?

Size_comparison_of_scansoriopterygid_dinosaurs

Illustration by Matthew Martyniuk. 1.8 m human, Yi qi (green), Epidexteryx hui (orange), Scansoriopteryx heilmanni (red)

That depends on what you consider a dinosaur. Anchiornis was estimated to be 34 cm (13″) long, but was a young adult, so probably got at least 38 cm (15″). But some consider Anchiornis to be an avialan, the earliest group of birds. Parvicursor is the smallest known adult dinosaur that is definitely not a bird according to some people, at 39 cm. Epidextipteryx was only 44 cm (17″) if you include the tail feathers, but only 25 cm(10″) if you don’t include them. However, Scansoriopteryx, also known as Epidendrosaurus, was only about 16 cm (6″), but we only have young ones that would have grown larger, but we don’t know how much larger. Epidextipteryx and Scansoriopteryx may look like birds, but were actually in a different group of dinosaurs. If you consider modern birds, the bee hummingbird takes the prize as the smallest known dinosaur at less than 6 cm (2.5″) and weighing less than 2 grams, just over the weight of a single penny.

But if you are talking about shortest, meaning how tall they stood, that is harder to work out because it would depend on how they stood, but none of these animals would have stood taller than 20cm (8″) at most.

For comparison, these dinosaurs were about the size of a common crow or perhaps even smaller.

Can an 8 feet tall person be as tall as a dinosaur?

A person standing 8 feet tall would be taller than a lot of dinosaurs. A baby just learning to walk would be bigger than some dinosaurs. If we include modern birds, which are also dinosaurs, there are some dinosaurs that a new born baby could hold in their hands (the bee hummingbird is less than 2.5″ long and more than an inch of that is taken up by the beak and tail feathers).

When did the dinosaurs live? When were they born?

nyasaurusmarkwitton

Nyasaurus, illustration by Mark Witton

The earliest known dinosaur is Nyasaurus, which was found in rocks thought to be 243,000,000 million years old during the Triassic Period, the first part of the Mesozoic Era. There is some uncertainty if this was an actual dinosaur, so if it wasn’t, that would make dinosaurs like Herrerosaurus and Eorapter (both of which looked similar to Nyasaurus) the oldest dinosaurs at about 230,000,000 years old.

When did the dinosaurs die?

Everything that most people call dinosaurs died out at the end of the Cretaceous Period, the third part of the Mesozoic Era, about 65,500,000 years ago. However, they didn’t all die out. One small group of dinosaurs survived, which are the birds. Today, birds are the most diverse group of terrestrial vertebrates (animals with a backbone living on land), so dinosaurs are alive and thriving.

How long did the dinosaurs live?

Dinosaurs were on earth for a very long time. From their beginnings over 240 million years ago to the end of the Cretaceous Period, they lived for around 175,000,000 years. If you include the birds, they have lived for over 240,000,000 years and are still going strong.

If you are talking about individual dinosaurs, they have varied lifespans. Just as you can find mammals that live no more than a year or so to mammals like us that can live over a hundred years old (the oldest known person lived to 122), you can find dinosaurs that lived like that. Some species of hummingbirds only live a few years, so we can expect that some other dinosaurs may have only lived a few years as well. The giant, long-necked sauropods were adults by their teens and may have lived as long or longer than we do. We reall

How old are T. rexes?

If you mean how long ago did they live, Tyrannosaurus rex lived at the very end of the Cretaceous Period, the last period of the Mesozoic Era, 68,000,000-65,500,000 years ago. If you wanted to know how old an individual T. rex could get, They did most of their growing when they were between 14-18 years old, reaching maturity between 16-18 years old. But they didn’t live long after that. All of them that we know of died before they were 30. Of course, whether or not they could have lived longer than that, we don’t know, but that is the ages of the fossils that we have.

How did the dinosaurs die?

Most of the dinosaurs died out at the end of the Cretaceous Period about 65,500,000 years ago when two major events happened. The first was eruption of one of the largest volcanic events in the history of the Earth. The volcanoes that formed the Deccan Traps in India were so massive, the rocks from the lava put out by these volcanoes are over 6000 feet deep. These eruptions happened over tens of thousands of years, maybe even millions of years.

But that wasn’t the worst thing. An asteroid hit in Mexico at the same time as the volcanic eruptions were taking place. It was estimated to be about 10 kilometers (6 miles) across and left a crater more than 100 miles across. Remnants of the crater can still be seen in Chicxulub, Mexico. If all the nuclear bombs in the world were exploded at the same time, it would not be as powerful as the impact of that asteroid.

Did some animals live after the volcano and meteor?

Amazingly enough, yes. If they had not, we would not be here. Every form of animal suffered heavy losses, but most did not die out completely. One small group of dinosaurs survived, which became the birds. A lot of mammals died out, but a lot also survived. Amphibians and crocodilians did reasonably well. Anything small, able to take shelter, and lie dormant (like squirrels hibernating in the winter) to conserve their energy and ride out the tough times did ok. In the oceans, anything large, needing a lot of food, or having shells had a hard time.All the large sea-going reptiles died out. Virtually all the shelled cephalopods (squid relatives) went extinct, but their unshelled relatives survived. Tiny organisms called plankton that lived in the ocean and made their shells out of calcium carbonate died out and were replaced by types that used silicon for shells. During the Cretaceous, the ones with carbonate shells were so common, when they died, their shells piled up and became huge layers of chalk, forming what became the famous White Cliffs of Dover in England and the chalk beds in southwestern Arkansas, among other places. But they almost all died out during the volcano and meteor impact and never became nearly as abundant ever again. The reason for this is because the asteroid and volcanoes released so much carbon dioxide and sulfur into the air that was soaked up by the oceans that the oceans became very acidic and lost a lot of oxygen. So anim

Of course, insects of all sorts survived, as did a variety of invertebrate animals like snails, clams, starfish and the like. But all of them took severe losses, especially those that were specialized to eat only certain plants or animals. One that had a more varied diet managed to survive.

How was it there? Was it dusty or cold there?

During the Mesozoic Era, the time of the dinosaurs, it was, in general, warmer than it is now and the temperature differences between seasons were not as extreme as today. The north and south poles were not permanently frozen over during this time like they are now. But much like today, there were all types of weather and environments. It was hot and dry in some places, it snowed in other places. There were swamps and prairies, forests, deserts, almost any environment you can think of existed then. The only environment you might not find would be glaciers, but you could probably even find them near the tops of mountains at times. Of course, they didn’t exist in the same place on earth and there were different dinosaurs that lived in different areas.

Also remember that the Mesozoic covered an immense span of time, so the earth changed during this time.

Why didn’t the dinosaurs need to fly?

Some dinosaurs did fly, but most didn’t. Most animals today don’t fly either. I expect most animals would if they could, but it takes a lot of changes to evolve the ability to fly. As animals evolve, they can’t decide they are going to develop flight. Small changes will appear in individuals from time to time and if those changes are helpful (or at least not harmful), then they get passed on and can spread through the population. To develop flight, a large number of changes have to happen, so only a few types of animals have evolved in the right way to develop flight. Once they did though, it was very effective, which we can tell by looking at the large number of birds and insects and even bats that can fly.

Is it true that fish had sting rays?

Southern-stingray-dorsal-viewThere are some fish called stingrays and they do indeed have venomous spines on the tail, which can be painful and occasionally deadly if they sting someone. They only use them in self defense though, so they won’t hurt anyone unless they feel threatened.

Stingrays are common today and can be seen in many aquariums. But they are also found as fossils and have been around for millions of years. We have even found fossils of stingrays in Arkansas. They do not have bones like we do, but we do find lots of their teeth, which look like flat rectangles. They use these flat teeth for crushing shells of clams and other animals.

What was the tiny thing at the bottom of the smart board?

I’m sorry, I don’t know what you are referring to. Was it on the timeline? Please let me know and we can figure it out.

How many bones have you found?

I have found lots of shells and crinoids. I have found a handful of shark teeth. But I haven’t found too many bones. When I was on a dig in Argentina, I did find a pelvis (hip bones) of a sauropod (the giant, long-necked dinosaurs). I also found part of a skeleton of an archosauromorph (the ancestors of crocodiles and dinosaurs). When I worked in Wyoming and Colorado, I found several fossil turtle shells and part of the horn of what may have been a uintathere or some similar animal (rhino-like mammals with knobby horns and bumps on their heads). I also found several tiny bones of rat-sized mammals. I don’t know what they were, but I remember one place where the bones looked like turquoise (a greenish-blue gemstone).

What I would really like to find would be a dinosaur in southwestern Arkansas, although the skull of a mosasaur or elasmosaurus would be a close second. There are opportunities for finding fossils in most of the state, so keep looking and let me know if you find something!


2 Comments

  1. albertonykus says:

    Including seabirds, a good case can be made that the least storm petrel (Halocyptena microsoma) is the smallest marine dinosaur.

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